It sucks when there is the need, no doubt. I would guess that at any given time of day JFK has the population of a small to medium city (tens to a hundred thousand?) people (passengers, staff, family members, etc) on the ground in the immediate response area of the airport paramedics (if such are dedicated), without taking into account inbound emergencies. EMS crews, even dedicated to the facility, can't just abandon a patient once contact has been without transferring care to an appropriate other provider, even if the first injury is of less priority than the inbound emergency.
Were the requested medical resources prior-committed? Was there a mechanical issue that slowed the response, or an emergency on their own responding crew, so another one (more distant) had to be sent? It happens, unfortunately.
Many on this website are property-owners who pay taxes for a range of public services, from administrative/governmental through police/fire/EMS and a host in-between. The balancing act between income and expense generally comes at the expense of public safety, rather than administrative support services. Who wants to pay more for increased staffing against the need it will be THEIR loved one or property at risk? It's a crap shoot, honestly, more often than most people realize.
It may be safer for a community to field three (or three hundred) cops per shift, but two (or two hundred) can usually handle the need. Six medics at the airport may provide a quicker response or redundancy when need exists, but four are less expensive and usually sufficient. Volunteers need time after dispatch to get to the rigs and then drive to the scene, but paid staff in sufficient numbers cost tax dollars no one really wants to pay until it's THEIR house on fire.
Unfortunately, the exact time of your emergency COULD be the moment the nearest timely resource is already committed to someone else's need.